WO2005070981A1

WO2005070981A1 - Low-solvent, oh-functional dispersions (ii)

Info

Publication number: WO2005070981A1
Application number: PCT/EP2005/000303
Authority: WO
Inventors: Martin Melchiors; Thomas MÜNZMAY; Thomas Stingl; Hartmut Ottensmann; Heinz-Dietmar Gewiss
Original assignee: Bayer Materialscience Ag
Priority date: 2004-01-27
Filing date: 2005-01-14
Publication date: 2005-08-04
Also published as: US7199178B2; CN1914237A; DE502005004627D1; EP1711545A1; EP1711545B1; US20050165145A1; ATE400595T1; CN100537625C; AU2005206263A1; ES2309712T3; MXPA06008252A; DE102004003894A1

Abstract

The invention relates to aqueous, hydroxy-functional binder dispersions having a low solvent content which are based on hydroxy-functional copolymers. The invention also relates to a method for producing said binders, to binder combinations on the basis thereof and to the use of the binders in lacquers.

Description

Low-solvent, OH-functional dispersions II

The invention relates to aqueous, hydroxy-functional binder dispersions with a low solvent content based on hydroxy-functional copolymers, a process for the preparation of such binders, binder combinations based on this and the use of the binders in paints.

It is known in coating systems (Paint & Resin 12/83, p. 34 ff., DE-A 3 209 421, EP-A 95 263, EP-A 105 293, EP-A 133 949, EP-A 288 763 and literature cited there) to use water-dilutable binders based on copolymers. However, these generally contain emulsifiers for stabilization and / or larger proportions of organic cosolvents.

The emulsifiers usually influence the properties of the paints or coatings, e.g. Water resistance, film optics (gloss), pigmentability negative.

The use of large amounts of organic solvents is undesirable for ecological reasons. However, it cannot be avoided in order to ensure sufficient stirrability and heat dissipation of the reaction mixture and a certain minimum degree of filling of the reactor during the preparation of the polymer. In addition, organic solvents in aqueous coating agents lead to advantageous effects such as improved storage stability, pigment wetting, film appearance and flow.

Subsequent reduction of process-related solvents from copolymers or dispersions is associated with high outlay in terms of apparatus and energy and thus also high costs, so that there is a need for aqueous polymer dispersions, the use of which is largely dispensed with in the manufacture of organic solvents, without any deterioration the application properties occur.

Copolymer dispersions which are to be cured by a chemical reaction, for example with an aminoplast resin, a blocked polyisocyanate or a polyisocyanate, must contain a certain amount of reactive groups, for example hydroxyl groups. These groups are generally introduced into the copolymer by the use of hydroxy-functional (meth) acrylic acid esters in the copolymerization. However, these raw materials are very expensive compared to the non-functional (meth) acrylic acid esters or also to styrene. In addition, larger amounts of these raw materials often have to be used in comparison to organically dissolved copolymers in order to compensate for the hydrophilicity of the coating films by means of a greater crosslinking density. The teaching of EP-A 0 758 007 shows a way of producing hydroxy-functional secondary copolymer dispersions which largely avoids the use of solvents in the polymerization. According to this document, the solvents usually used are completely or partially replaced by hydroxy-functional polyethers. The hydroxy-functional polyethers remain as reactive diluents in the secondary dispersion and react later with isocyanates or blocked isocyanates to form urethane. You are not contributing to the VOC. A disadvantage of these products is their poor durability.

It has now been found that aqueous copolymer dispersions with a low solvent content and high resistance level of the coating films can be produced based on hydroxy-functional copolymers if hydroxy-functional components of the formula (I):

in the

R ^{1 is} an aliphatic, araliphatic or aromatic radical with 1 to 18 carbon atoms,

R ^{2 is} H or CH ₃ ,

R, R4 are the same or different aliphatic radicals having 1 to 7 carbon atoms and

n is 1 to 4,

can be used as reactive diluents.

The invention therefore relates to a process for the preparation of copolymer dispersions, in which

A) one or more vinyl monomer mixtures containing a) OH-group-free (meth) acrylic acid esters and / or vinyl aromatics, b) hydroxy-functional vinyl monomers or hydroxy-functional (meth) acrylic acid esters, c) ionic and / or potentially ionic monomers capable of free radical copolymerization and d) optionally further monomers capable of free radical copolymerization other than the compounds of components a) - c) in the presence of e) compounds of the formula (I)

in the

R ^{2 is} H or CH ₃ ,

R ³ , R ^{4 are the} same or different aliphatic radicals having 1 to 7 carbon atoms and n is 1 to 4, are polymerized by free radicals and the copolymer thus obtained is then

B) before or after adding a neutralizing agent

C) is dispersed in water.

The invention further relates to the aqueous copolymer dispersions obtainable by the process described above.

As monomers of component a), acrylates and methacrylates (hereinafter referred to as (meth) acrylates) with 1 to 18 carbon atoms in the alcohol part of the ester group are used. This alcohol part can be linear, branched or cycloaliphatic. Suitable as monomers of component a) are, for example, methyl, ethyl, n-propyl, n-butyl, isopropyl, isobutyl, t-butyl, the isomeric pentyl, hexyl, 2-ethylhexyl, octyl -, Dodecyl-, Hexadecyl-, Octadecyl- or Cyclohexyl-, Trirnethylcyclohexyl- and Isobornyl- (meth) acrylates.

Furthermore, acetoacetoxyethyl methacrylate, acrylamide, acrylonitrile, vinyl ether, methacrylonitrile, vinyl acetates, optionally substituted styrenes and vinyl toluenes can also be used in a).

It is also possible to use any mixtures of the abovementioned compounds in component a).

In component b) it is possible to use ethylenically unsaturated monomers containing OH groups, such as, for example, hydroxyalkyl esters of unsaturated carboxylic acids, preferably hydroxyalkyl (meth) acrylates having 2 to 12, preferably 2 to 6, carbon atoms in the hydroxyalkyl radical.

Examples of such compounds are 2-hydroxyethyl (meth) acrylate, the isomeric hydroxypropyl (meth) acrylates, 2-, 3- and 4-hydroxybutyl (meth) acrylates and the isomeric hydroxyhexyl (meth) acrylates.

(Meth) acrylates in the context of the present invention are always to be understood as meaning both the acrylates in question and also methacrylates.

Likewise in b), polymerizable hydroxy-functional monomers modified or chain-extended with alkylene oxides and having a number-average molecular weight of <3,000 g / mol, preferably <500 g / mol, can be used. As alkylene oxides, ethylene, propylene or butylene oxide are preferably used individually or in mixtures.

As ionic and / or potentially ionic monomers of component c) capable of radical copolymerization, olefinically unsaturated monomers with carboxylic acid or carboxylic anhydride groups, such as e.g. Acrylic acid, methacrylic acid, β-carboxyethyl acrylate, crotonic acid, fumaric acid, maleic anhydride, itaconic acid or monoalkyl esters of dibasic acids or anhydrides such as e.g. Maleic acid monoalkyl esters are used, preferably acrylic acid and / or methacrylic acid.

Also suitable as compounds of component c) are also unsaturated, free-radically polymerizable compounds with phosphate or phosphonate or sulfonic acid or sulfonate groups, as described, for example, in WO-A 00/39181 (p. 8 lines 13- p 9 line 19), in particular 2-acrylamido-2-methylpropanesulfonic acid. Optionally, other monomers capable of free radical copolymerization can also be used as compounds of component d). These can be, for example, di- or higher-functional meth) acrylate monomers and / or vinyl monomers, such as, for example, hexanediol di (meth) acrylate or divinylbenzene. It is also possible to add polymerizable, non-ionically hydrophilizing compounds such as acrylates of hydroxy-functional polyalkylene oxide ethers.

The quantitative ratios of the structural components a) to d) are typically chosen such that an OH number of 12 to 200 mg KOH / g, preferably 25 to 150 mg KOH / g and particularly preferably 50 to 150 mg KOH / g solid and an acid number of 0 to 50 mg KOH / g, preferably 10 to 30, particularly preferably 15 to 25 mg KOH / g of solid results.

Based on the copolymer, preference is given to 50-85% by weight of component a), 15-40% by weight of component b), 0.5-5% by weight of component c) and 0-34.5% by weight. Component d) is selected so that copolymers are obtained which correspond to the above information with regard to OH and acid number.

Compounds of formula (I) are preferably used in e), wherein

Rl 2 to 6 carbon atoms and

R ³ , R ^{4 contains} 1 to 7 carbon atoms

R ^{2 is} H or CH ₃ and

n is 1 to 4.

Compounds of formula (I) are particularly preferably used in e), wherein

R * 2 or 4 carbon atoms and

R ³ , R ^{4 contains} 1 to 7 carbon atoms,

R ^{2 is} CH ₃ and

n is 2.

The reaction products of gycidyl esters of aliphatic carboxylic acids (el)) with aliphatic, araliphatic or aromatic carboxylic acids (e2)) are suitable as component e). Preferred compounds of component el) for this case are acid Gycidylester of versatic, which are available for example as Cardura E10P from Resolution BV ^®., Netherlands.

Preferred compounds of component e2) for this case are saturated aliphatic monocarboxylic acids such as acetic, propionic, butteric, pentane, hexane, heptane, octane, 2-ethylhexane, nonane, decahole, lauric , Myristic, palmitic, margaric, stearic, arachic, behenic, lignoceric acid or unsaturated monocarboxylic acids such as oleic, linoleic, linolenic, ricinoleic acid or aromatic monocarboxylic acids such as benzoic acid, aliphatic di- or polycarboxylic acids such as succinic , Glutaric, adipic, pimeline, cork, azelaic, sebacic, nonandicarboxylic, decanedicarboxylic, dimer fatty acids, which can be obtained by dimerizing unsaturated monocarboxylic acids, aromatic di or polycarboxylic acids such as, for example, terephthalic, isophthalic, o -Phthalic, tetrahydrophthalic, hexahydrophthalic or trimellitic acid. Mixtures of the compounds mentioned can of course also be used in component e2).

It is particularly preferred to use glycidyl esters of versatic acid as el) in combination with aliphatic monocarboxylic acids such as 2-ethylhexane, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid and behenic acid and unsaturated monocarboxylic acids such as oleic acid, linoleic acid -, Linolenic, ricinoleic acid and dicarboxylic acids such as succinic and adipic acid or the isomeric phthalic acids as e2). Adipic acid is particularly preferably used in e2).

The compounds of component e) can be prepared from components el) and e2) before or simultaneously to the free-radical polymerization of the unsaturated monomers a) to d).

The temperatures are typically 50 to 200 ° C, preferably 90 to 140 ° C. The compounds of component e) are preferably prepared from el) and e2) before the radical polymerization of the unsaturated components a) to d).

The amount of component e) in relation to the sum of the amounts from a) to e) is typically 5 to 60% by weight, preferably 10 to 30% by weight and particularly preferably 15 to 30% by weight.

The procedure for the polymerization of the unsaturated monomers is familiar to the person skilled in the art. Typically, the reactive diluents e) or the structural components of the reactive diluents el) and e2) are initially introduced into a reaction vessel and the unsaturated monomers are polymerized using a radical initiator.

If necessary, additional organic solvents can be used in a minor amount. Suitable auxiliary solvents are any solvents known in coating technology, such as, for example, alcohols, ethers, alcohols containing ether groups, esters, ketones, N-methylpyrrolidone or non-polar hydrocarbons or mixtures of these solvents. The solvents are used in amounts such that their content in the finished dispersion is 0 to 5% by weight. If necessary, the solvents used can be partially removed again by distillation. In a preferred embodiment, however, no additional organic solvents are used.

The copolymerization is generally carried out at 40 to 200 ° C, preferably at 60 to 180 ° C, particularly preferably at 80 to 160 ° C.

Organic peroxides such as di-tert-butyl peroxide or tert-butyl peroxy-2-ethylhexanoate and azo compounds such as azodiisobutyronitrile (AIBN) are suitable as initiators for the polymerization reaction. The amounts of initiator used depend on the desired molecular weight. For reasons of process reliability and easier handling, peroxide initiators can also be used as a solution in suitable organic solvents of the type mentioned above.

In a preferred embodiment of the process, a two-stage addition and polymerization of unsaturated monomers of the type mentioned above takes place in the presence of component e). In a first step (I), a hydroxy-functional copolymer with an OH number of 12 to 200 mg KOH / g solid and an acid number of 0 to 50 mg KOH / g solid consisting of 55-90% by weight of component a) , 2.5 - 50 wt .-% component b), 0 - 6.5 wt .-% component c) and 0 - 42.5 wt .-% component d). In a subsequent step (IT), a further polymer is prepared from monomers of components a) - d) in the reaction mixture obtained from step (I), this polymer having an OH number of 20 to 200 mg KOH / g solid and an acid number from 50 to 200 mg KOH / g solid. The polymer from step (TJ) consists of 45-80% by weight of component a), 5-50% by weight of component b), 6.5-25% by weight of component c) and 0-43.5 % By weight component d). The percentages of the polymer composition add up to 100% by weight per polymer. The monomer amounts of the two polymer preparations are to be selected so that the mass ratio of the polymer from step (I) to that from step (II) is 10: 1 to 1: 2, preferably 6: 1 to 2: 1.

Instead of a multi-stage polymerization process, it is also possible to carry out the process continuously (gradient polymerization), ie a monomer mixture with a composition that changes according to the composition of the copolymer (s) A) is added, the hydrophilic monomer components preferably being added according to components c) and optionally d) towards the end of the inflow are higher than at the beginning. The copolymers obtainable by the process according to the invention have number average molecular weights M _n of 500 to 30,000 g / mol, preferably 1,000 to 15,000 g / mol, particularly preferably 1,500 to 10,000 g / mol.

Before, during or after the dispersion of the hydroxy-functional copolymers A) in water (step C)), the acid groups present are converted into their salt form at least in part by adding suitable neutralizing agents (step B)). Organic amines or water-soluble inorganic bases are suitable as neutralizing agents, such as soluble metal hydroxides, carbonates or bicarbonates.

Examples of suitable amines are N-methylmorpholine, triethylamine, ethyldiisopropylamine, N, N-dimethylethanolamine, N, N-dimethylisopropanolamine, N-methyldiethanolamine, diethylethanolamine, triethanolamine, butanolamine, mo holin, 2-aminomethyl-2-methylpropanol or isophoronediamine. Proportionate ammonia can also be used in mixtures. Triethanolamine, N, N-dimethylethanolamine and ethyldiisopropylamine are particularly preferred.

The neutralizing agents are added in B) in amounts such that in total there is a theoretical degree of neutralization [of the acid groups] of 40 to 150%, preferably 60 to 120%. The degree of neutralization is understood as the ratio of added basic groups of the neutralization component from B) to acid functions of the copolymer. The pH of the aqueous binder dispersion according to the invention is 6 to 10, preferably 6.5 to 9.

The aqueous, hydroxy-functional binder dispersions according to the invention have a solids content of 25 to 70% by weight, preferably 35 to 60% by weight, particularly preferably 50 to 59% by weight, and an organic solvent content of 0 to 12% by weight .-%, preferably 1 to 3.5 wt .-%.

The binder dispersions according to the invention can be processed into aqueous coating compositions. By combining with crosslinkers, depending on the reactivity or blocking of crosslinkers, both one-component and two-component coatings can be produced. In the context of the present invention, one-component lacquers are to be understood as coating compositions in which the binder component and crosslinker component can be stored together without a crosslinking reaction taking place to an appreciable extent or harmful to later application. The crosslinking reaction only takes place after application after activation of the crosslinker. This activation can be effected, for example, by increasing the temperature. Two-component lacquers in the sense of the present invention are coating agents in which the binder component and crosslinker component are stored in separate vessels due to their high reactivity have to. The two components are mixed shortly before application and then generally react without additional activation. To accelerate the crosslinking reaction, however, catalysts can also be used or higher temperatures can be used.

The present invention therefore also provides at least aqueous coating compositions

i) one or more copolymer dispersions according to the invention and

ii) at least one OH group-reactive crosslinker.

Suitable OH group-reactive crosslinkers are, for example, polyisocyanate crosslinkers, amide and amine formaldehyde resins, phenolic resins, aldehyde and ketone resins, such as e.g. Phenol-formaldehyde resins, resols, furan resins, urea resins, carbamic acid ester resins, triazine resins, melamine resins, benzoguanamine resins, cyanamide resins, aniline resins, as described in "Lackkunstharze", H. Wagner, H.F. Sarx, Carl Hanser Verlag Munich, 1971.

Blocked polyisocyanates are preferably used as crosslinkers. Such polyisocyanates typically have 2 or more NCO groups per molecule and are based, for example, on isophorone diisocyanate, hexamethylene diisocyanate, 1,4-diisocyanatocyclohexane, bis (4-isocyanatocyclohexane) methane, 1,3-diisocyanatobenzene, triisocyanatononane or the isomeric 2,4- and 2,6-TDI and may also contain urethane, isocyanurate and / or biuret groups.

It is particularly preferred to use low-viscosity, optionally hydrophilized, polyisocyanates of the aforementioned type based on aliphatic or cycloaliphatic isocyanates.

The polyisocyanates used as crosslinking agents generally have a viscosity of 10 to 5,000 mPas at 23 ° C. and can also be used in a mixture with small amounts of inert solvents if desired to adjust the viscosity.

The copolymers essential to the invention are generally sufficiently hydrophilic that hydrophobic crosslinking resins can also be dispersed without additional emulsifiers. However, this does not rule out the use of external emulsifiers.

Water soluble or dispersible polyisocyanates are e.g. by modification with carboxylate,

Sulfonate and or polyethylene oxide groups and or polyethylene oxide / polypropylene oxide groups available. Hydrophilization of the polyisocyanates is possible, for example, by reaction with undersized amounts of monohydric, hydrophilic polyether alcohols. The manufacture of such Hydrophilized polyisocyanates are described, for example, in EP-A 0 540 985 (page 3, line 55 to page 4 line 5).

The allophanate groups described in EP-A 959 087 (p. 3 lines 39 to 51) are also very suitable and are prepared by reacting low-monomer polyisocyanates with polyethylene oxide polymer alcohols under allophanatization conditions. The water-dispersible polyisocyanate mixtures based on triisocyanatononane described in DE-A 100 078 21 (p. 2 lines 66 to p. 3 line 5) are also suitable, and polyisocyanates hydrophilized with ionic groups (sulfonate, phosphonate groups), such as they are eg are described in DE 100 24 624 (p. 3 lines 13 to 33).

In principle, it is of course also possible to use mixtures of different crosslinking resins.

Before, during or after the preparation of the aqueous, hydroxy-functional binder dispersion according to the invention, the customary auxiliaries and additives can be added to coating technology, such as Defoamers, thickeners, pigments, dispersing aids, catalysts, skin-preventing agents, anti-settling agents or emulsifiers.

These auxiliaries and additives can also be added to the coating composition containing the aqueous, hydroxy-functional binder dispersions according to the invention.

The aqueous coating compositions containing the aqueous, hydroxy-functional copolymer dispersions according to the invention are suitable for all fields of application in which aqueous coating and coating systems with high demands on the durability of the films are used, e.g. for coating mineral building material surfaces, painting and sealing wood and wood-based materials, coating metallic surfaces (metal coating), coating and painting asphalt or bituminous coverings, painting and sealing various plastic surfaces (plastic coating) as well as high-gloss paints.

Since coating compositions containing the copolymer dispersions essential to the invention lead to coatings with a very high level of properties, they are also suitable for producing crack-bridging coatings, preferably in the construction sector and on mineral substrates.

The aqueous coating compositions containing the aqueous, hydroxy-functional binder dispersions according to the invention are used for the production of primers, fillers, pigmented or transparent topcoats, clearcoats and high-gloss lacquers and single-layer lacquers which are used in single and series application, for example in the field of industrial painting, for the automotive industry and repair paintwork can be used. It is preferred to use the aqueous coating compositions comprising the aqueous, hydroxy-functional binder dispersions according to the invention for coating or painting mineral surfaces, wood and plastics.

The coating compositions of the invention are typically cured at temperatures from 0 to 140 ° C., preferably from 18 to 80 ° C.

With very good film optics, these coatings have a high level of resistance to solvents and chemicals, good weather resistance, high hardness and fast drying.

The coatings can be produced using the various spraying processes, such as air pressure, airless or electrostatic spraying processes, using one- or, if appropriate, two-component spraying systems. However, the lacquers and coating compositions comprising the aqueous, hydroxy-functional dispersions of the invention can also be applied by other methods, for example by brushing, rolling or knife coating.

Examples:

Unless otherwise stated, all percentages relate to percent by weight.

From Physica, Stuttgart, Germany in accordance with DIN 53019 Viscosity measurements were determined using a cone-plate viscometer Pysica Viscolab ^® LC3 ISO performed at a shear rate of 40 s ^".

The determination of the average particle size by means of laser correlation spectroscopy (Zetasizer ^® 1000, Malvern Instruments, Herrenberg, Germany).

The OH numbers given were calculated on the basis of the monomers used.

Acid numbers: determination method, DIN ISO 3682

Cardura ^® ElOP: Glvcidvlester of versatic acid. Resolution BV., NL

Dowanol ^® PnB: propylene glycol n-butyl ether, Dow Chemical, Midland, United States.

Peroxan ^® DB: di-tert-butyl peroxide, Pergan GmbH, Bocholt, Germany.

Example 1 Reactive Thinner

In a 5 1 reactor equipped with a stirring, cooling and heating apparatus was weighed at 20 ° C 3172 g of Cardura ^® elop and 927 g of adipic acid. The mixture was heated to 140 ° C. with stirring. An exothermic reaction took place from approx. 140 ° C. The mixture was stirred at 140 ° C. for a further 4 hours. A light yellow resin with a viscosity of 2,900 mPas at 23 ° C. was obtained.

Example 2 Reactive Thinner

3172 g of Cardura® ElOP and 1054 g of isophthalic acid were weighed into a 5 l reaction vessel with a stirring, cooling and heating device at 20 ° C. The mixture was heated to 160 ° C. with stirring. An exothermic reaction took place from approx. 150 ° C. The mixture was stirred at 160 ° C. for a further 6 hours. A light yellow resin with a viscosity of 150,000 mPas at 23 ° C. was obtained.

Example 3

600 g of reactive diluent according to Example 1 were placed in a 6 1 reaction vessel with a stirring, cooling and heating device and heated to 148 ° C. At this temperature a solution of 8.25 g of di-tert-butyl peroxide in 8.25 g of Dowanol ^® PnB was added dropwise over 20 min.

Subsequently, a monomer mixture of 365 g methyl methacrylate, 854 g hydroxy ethyl methacrylate, 600 g butyl acrylate and 480 g sryrol and, in parallel, a solution of 28.5 g di-tert-butyl peroxide in 28.5 g Dowanol ^® PnB were evenly metered in over 4.5 hours. It was held at this temperature for about 20 minutes. This was followed by a monomer mixture of 122.25 g of methyl methacrylate, 172.75 g of hydroxyethyl methacrylate, 96 g of butyl acrylate and 84 g of acrylic acid and, in parallel, a solution of 8.25 g of di-tert-butyl peroxide in 20.75 g of Dowanol ^® PnB evenly metered in within 1.5 hours. Then stirred for 1 hour at 148 ° C, then cooled to 100 ° C and 174 g of triethanolamine added. After homogenization for 30 minutes, the mixture was dispersed with 2050 g of water at 80 ° C. in the course of 2 hours. A copolymer dispersion was obtained with the following data:

OH content (solid, theoretically calculated) 5.9%

Acid number (solids) 23 mg KOH / g

Solids content 50%

Viscosity 2,600 mPas / 23 ° C

pH (10% in water) 7.5

Degree of neutralization 100%

Average particle size 115 nm

Example 4

600 g of reactive diluent according to Example 2 were placed in a 6 1 reaction vessel with a stirring, cooling and heating device and heated to 148 ° C. At this temperature a solution of 8.25 g of di-tert-butyl peroxide in 8.25 g of Dowanol ^® PnB was added dropwise over 20 min. Following this, a monomer mixture of 365 g of methyl methacrylate, 854 g hydroxyethyl methacrylate, 600 g butyl acrylate and 480 g styrene was and parallel, a solution of 28.5 g of di-tert-butyl peroxide in 28.5 g Dowanol PnB ^® within 4, Dosed evenly for 5 hours. It was held at this temperature for about 20 minutes. This was followed by a monomer mixture of 122.25 g of methyl methacrylate, 172.75 g of hydroxyethyl methacrylate, 96 g of butyl acrylate and 84 g of acrylic acid and, in parallel, a solution of 8.25 g of di-tert-butyl peroxide in 20.75 g of Dowanol ^® PnB evenly metered in within 1.5 hours. Then stirred for 1 hour at 148 ° C, then cooled to 100 ° C and 174 g of triethanolamine added. After 30 minutes of homogenization, the mixture was dispersed with 2050 g of water at 80 ° C. in the course of 2 hours. A copolymer dispersion was obtained with the following data: OH content (solid; theoretically calculated) 3.3%

Acid number (solids) 23 mg KOH / g

Solids content 50%

Viscosity 1,700 mPas / 23 ° C

pH (10% in water) 7.5

Degree of neutralization 100%

Average particle size 115 nm

Example 5: Comparison

(EP-A 0 758, 007, example 1)

6 in a 1 l reaction vessel with a stirring, cooling and heating device, 116 g of butyl glycol and 150 g of Desmophen ^® V218 (polyether based on propylene oxide and glycerol, OH number 245 mg KOH / g, Bayer AG Leverkusen, DE) were provided and heated to 155 ° C. At this temperature, 321 g of butyl acrylate, 366 g of styrene and 198 g of hydroxyethyl methacrylate were metered in over the course of 2 hours and, in parallel, a solution of 17.1 g of di-tert-butyl peroxide in 28.6 g of butyl glycol. Subsequently, a monomer mixture of 83 g of hydroxyethyl methacrylate, 180 g of butyl acrylate, 139 g of styrene and 34 g of acrylic acid was metered in over the course of 1 hour and, in parallel, 12.9 g of di-tert-butyl peroxide in 21.4 g of butyl glycol. Then stirred for 2 hours at 150 to 155 ° C, then cooled to 100 ° C and 50 g of dimethylethanolamine added. After homogenization for 30 minutes, the mixture was dispersed with 80 g of water at 80 ° C. in the course of 2 hours. A copolymer dispersion was obtained with the following data:

OH content (solid; theoretically calculated) 3.2%

Acid number (solids) 18 mg KOH / g

Solids content 40%

Viscosity 830 mPas / 23 ° C

pH (10% in water) 9.4 Degree of neutralization 100%

Average particle size 51 ran

Solvent content 4.5%

Example 6: Resistance

To assess the resistance coating agent according to the table below (amounts in parts by weight) from the dispersions of Examples 3 and 5 and Bayhydur ^® XP 2451 Bayhydur ^® XP 2451 (hydrophilicized polyisocyanate based on HDI, Bayer AG, Leverkusen, DE) were prepared as crosslinkers, applied with a hand squeegee to a wooden board (beech) and cured for 24 h at room temperature.

Component Film A Film B dispersion of Example 3 100 dispersion from Example 5100 Bayhydur XP ^® 2451 20.6 20.8

Chemical resistance based on DIN 68861, 210 μm wet film

Medium and duration film A film B water I day 5/2 5/2 7 days 5/2 4/2 shoe polish 5 hours 5/2 4/2 red wine 5 hours 4/2 4/2 ethanol 98% 1 hour 4/0 3/0 ammonia, 12.5% 1 hour 5/2 4/2 isopropanol 1 hour 4/2 3/0 5 hours 4/1 dissolved

First value: staining

5 = no visible change; 0 = test area heavily changed or destroyed Second value: residual hardness

2 = unchanged; 0 = easy to remove mechanically

The binder according to the invention shows a significantly improved resistance to aggressive media, in particular to ethanol and isopropanol.

Example 7: Gloss

To evaluate the gloss properties coating agent according to the table below (amounts in parts by weight) of the dispersions of Example 3 and 5 and Bayhydur ^® XP 2451 (hydrophilicized polyisocyanate based on HDI, Bayer AG, Leverkusen, DE) were prepared as crosslinkers, with a manual knife a Leneta film (plastic film according to DIN 53775, black matt, 430 x 165 mm, B. Schwegmann GmbH, Gelsdorf, DE) is applied and cured for 24 hours at room temperature.

Component Film C Film D Dispersion from Example 3 100 Dispersion from Example 4 100 Bayhydur ^® XP 2451 20.6 20.8

Gloss in percent measured according to DIN 67 530 or ISO 2813 on clear lacquer; 200 μm wet film

Angle Fil C Film D 20 ° 77% 21%

60 ° 90% 55%

85 ° 98% 78%

The binder according to the invention resulted in lacquer films with a substantially higher gloss than the comparable binder according to the prior art.

Example 8: Film hardness

To assess the film hardness, coating agents were prepared from the dispersions of Examples 3 and 5 and Bayhydur ^® XP 2451 (2451 (Hydrophilized polyisocyanate based on HDI, Bayer AG, Leverkusen, DE) as a crosslinker, knife-coated with a hand knife onto a glass plate with a wet film thickness of 150 μm and cured for 24 hours at room temperature.

The film hardness was determined as the pendulum hardness according to DIN EN ISO 1522 (pendulum damping).

Component Film A Film B dispersion of Example 3 100 dispersion from Example 5100 Bayhydur XP ^® 2451 20.6 20.8 Pendulum hardness after 3 days [sec] 94 78 Pendulum Hardness after 7 days [s] 113 91

The comparison shows that the binders according to the invention are superior to the binders according to the prior art in terms of both the rate of hardness development and the final hardness.

Claims

claims:

1. Process for the preparation of copolymer dispersions, in which

A) one or more vinyl monomer mixtures containing a) OH group-free (meth) acrylic acid esters and / or vinyl aromatics, b) hydroxy-functional vinyl monomers or hydroxy-functional (meth) acrylic acid esters, c) ionic and / or potentially ionic monomers capable of radical copolymerization, and d) optionally further monomers capable of radical copolymerization different from the compounds of components a) - c) in the presence of e) compounds of the formula (I)

in which R * is an aliphatic, araliphatic or aromatic radical having 1 to 18 carbon atoms,

R ^{2 is} H or CH ₃ ,

B) before or after adding a neutralizing agent C) is dispersed in water.

2. A process for the preparation of copolymer dispersions according to spoke 1, characterized in that the polymers prepared in A) have an OH number of 50 to 150 mg KOH / g solid, an acid number of 15 to 25 mg KOH / g solid and a number have an average molecular weight M _n of 1,500 to 10,000 g / mol.

3. A process for the preparation of copolymer dispersions according to claim 1 or 2, characterized in that the polymers prepared in A) from 50-85% by weight of component a), 15-40% by weight of component b), 0.5- There are 5% by weight of component c) and 0-34.5% by weight of component d) and the amounts from the above ranges add up to 100% by weight.

4. A process for the preparation of copolymer dispersions according to any one of claims 1 to 3, characterized in that reaction products of gycidyl esters of aliphatic carboxylic acids with aliphatic, araliphatic or aromatic carboxylic acids are used in component e).

5. A process for the preparation of copolymer dispersions according to any one of claims 1 to 4, characterized in that the polymerization is carried out in two stages.

6. copolymer dispersions obtainable by a process according to any one of claims 1 to 5.

7. Use of the copolymer dispersions according to claim 6 in the production of coatings.

8. Aqueous coating compositions containing at least i) one or more copolymer dispersions according to claim 6 and ii) at least one OH group-reactive crosslinker.

9. Coatings obtainable from copolymer dispersions according to claim 6.

10. substrates coated with coatings according to claim 9.